For many years the trading of shares listed on a stock exchange were effected by the activities of people known as traders on the trading floor of a stock exchange, and were confirmed by some form of notation or writing on paper. Once effected, the trades or transfers of shares were formally reported to brokers for the purchasing and selling customers in a formal way with or without the delivery of the share certificates.
More recently the transactions have become automated so that trades may be done by a trader operating a keyboard to enter the necessary commands into a terminal connected to the mainframe computer of the stock exchange, or a small personal computer with a terminal emulator. With this automated system a trader may enter an order to buy or sell which is transmitted to the central system of the stock exchange where it matched with another trader who is willing to sell or buy the same shares, and the computer then confirms the completion of the transaction to each trader, and the transaction is confirmed and recorded by means of a hard copy generated on a printer.
Although this computerized automated system was much faster than the trading floor, it still required a trader to key in by hand the necessary data and commands for each individual stock being traded. From the information available at a terminal, the trader/operator would have to input the symbol for the company shares, the price, the exchange, the size of the order, and the instructions to buy, sell, cross or short trade the stock.
It has even become possible to effect trades in certain stocks automatically when they reach a certain price level.
However, modern investment strategies involve the investment in large groups or "basket" of listed shares as part of an entire portfolio which is strategically selected to provide a balance of growth potential, income generation, and risk avoidance. These portfolios are often held by mutual funds, banks, insurance companies, or other institutional investors, and they are frequently being changed to adjust the balance in the factors which effect growth, income and risks.
Some institutions invest in an established mixture of stocks which reflect the current economic climate in the country, such as the TSE 35, the TSE 100, the TSE 300, and in the United States the Dow Jones or other representative portfolios. In some cases institutional investors will establish their own collection of shares which it considers to represent their investment strategy and objectives. These may be weighted in favour of industry groups such as mining companies, financial institutions, manufacturing, or others considered preferable by the investment manager.
As a result of this strategy of investing in a mixed "basket" of shares, institutional investors are often increasing or decreasing their investment in the entire range of shares in a basket or index. This therefore requires a large number of trades in order to effect the single investment move. Hitherto, this has been done by a trader/operator keying in the necessary trades in each individual stock through a computer terminal. Where the portfolio includes a list of 100 stocks, for example, this is a lengthy process and in fact the problem arises that the prices of many shares would change during the time it takes to key in the various orders, and the original conditions necessary to satisfy the requirements of the particular trade may no longer be present.